In 1996, California was the first state to pass a Compassionate Use Act which allowed for the legal use of cannabis for medicinal or medical purposes. Despite leading the way for the use of cannabis in the treatment of many chronic disorders, little systematic research has been conducted that has examined how the opening and closing of these dispensaries change the ecological landscape of the neighborhoods in which they are located. The current application takes advantage of a natural experiment occurring in Los Angeles and Sacramento Cities to assess how both the growth of and subsequent reduction in these dispensaries has resulted in changes in crime and cannabis use and dependence over a thirteen-year period. The proposed research will examine the relationship between the density and location of these dispensaries, prices of marijuana and related products, and crime in multiple contexts. Further, use of portal surveys will enable us to understand the distance to which clients travel to obtain cannabis and the types of clients who use different dispensaries. Five specific aims will be tested: (1) Examine whether the density of cannabis dispensaries is related to increases in rates of violent and property crimes; (2) Examine whether the changing density of cannabis dispensaries is related to similar changes in rates of cannabis dependence and abuse; (3) Determine whether or not neighborhood characteristics (including location and density of other dispensaries) are related to price differences across dispensaries; (4) Investigate whether or not there is greater clustering by patron characteristics consistent with niche theory in high density areas; and (5) Determine whether or not patterns of medical cannabis use correspond to overall health levels and/or diagnosis of medical cannabis patients.